Many fuel injectors for turbine engines in use today include venturi-like constrictions in an air tube fitted about a fuel injection nozzle or the like. Fuel is delivered, via a manifold, to an atomizer fitting including the venturi. Typically, the manifold or fuel line is attached by an appropriate fitting to the case for the combustor of the engine and the atomizer fitting is brazed or welded to a combustor wall within the combustor case.
Within the fuel line, a metering orifice may be located to provide so-called "manifold head" compensation. The fuel line delivers fuel to a cavity within the atomizer fitting to one side of the venturi therein and, from the cavity a U-shaped fuel injecting tube delivers the fuel to the interior of the venturi. High velocity air from the engine compressor and directed to the space between the combustor wall and the combustor casing flows through the venturi within the atomizer fitting past the end of the U-shaped tube to atomize the fuel.
In the usual case, the fuel pressure is slightly above the air pressure between the combustor wall and the combustor casing and as a consequence, a seal must be provided between the atomizer fitting and the fuel line.
When the engine is shut-down, residual heat will soak the seal and raise the temperature substantially. Not infrequently, temperatures as high as 600.degree. F. may be attained.
Where the seal is an O-ring seal, as is typically the case, the same deteriorates with the consequence that fuel may leak into the space between the combustor wall and the combustor casing. Fuel leakage in any event is undesirable and, where compressor bleed air is utilized in an air conditioning system for an aircraft or the like, leaking fuel can cause fuel vapors to ultimately enter the aircraft cabin via the air conditioning system.
In addition, in structures of the type mentioned before, carbon build-up may occur on the end of the U-shaped fuel tube just upstream of the venturi throat This build-up may cause hot spots or hot streaks which are undesirable and which can cause damage to the engine Further, should the carbon break loose, it may cause damaging erosion to engine parts.
The present invention is directed to avoiding the problems associated with fuel leaks and carbon build-up. In addition, it is directed to improving atomization of fuel since improved atomization will provide for better engine starting as well as lesser exhaust smoke.